1. Field of the Invention
The invention relates to paperboard, corrugated or similar cartons and containers made in an automated manner by folding panels of an integral flat blank and gluing the panels at key locations. The container is supplied in a collapsed or knocked-down flat configuration. Before loading with product the container is erected manually into a rectilinear box by simple motions. Erection of the folded and glued panels produces certain useful structural attributes such as improved stacking strength, stack alignment, locking of the box in the erected state, etc.
2. Related Art
Corrugated and paperboard containers are made from one or more pieces of flat stock that are cut in required shapes and are assembled to form the walls of a full or partial enclosure. Variations are possible in which several separately-integral parts are formed and then are assembled using glue, tape, staples or the like. For example, the container body and lid may be separate parts, or various types of inserts may be used for reinforcement or other purposes such as subdividing the volume of the container into discrete areas.
Containers are supplied in a collapsed state because storage or handling of empty containers is wasteful of space. The containers are partly formed, with their parts cut out and certain seams and folds provided. The packer erects the containers prior to loading, and finishes any required assembly steps in the process. The loaded containers are finally closed, as suitable for storage or shipment. For example, a container may be cut out from integral flat stock, folded and scored at spaced parallel lines corresponding to the corners of the container (with at least one seam), and supplied with the opposite side and end walls collapsed flat against one another. Top and bottom flaps are likewise integrally attached to the side and end walls at folds or score lines. The packer erects the container from a flat parallelogram into its rectilinear shape, folding the bottom and top flaps inwardly before and after loading, respectively, and finally closing the container at seams that are taped, glued or otherwise attached.
It is efficient if most or preferably all of the container parts are integral parts and extensions of a single piece of flat material. Separate discrete parts such as separate lids, partitions and reinforcing inserts involve manual assembly steps. Manual assembly steps are costly and consume worker time in several ways. In addition, assembly steps can be physically taxing and may lead to repetitive motion injuries. It is preferable if containers are substantially fully formed when supplied, and require the least possible manual action to deploy, load, close and store or pack the containers for shipment. However it is also important for the containers to be structurally sound.
Self-erecting paperboard and corrugated containers are known with their respective wall panels and flaps connected in such a way that one or more of the structural parts of the container is pulled into an erected position as the other parts are erected. Commonly owned pending patent application Ser. No. 09/129,375, filed Aug. 5, 1998, entitled Stackable Container, discloses an integral blank container having folded and glued bellows or gusset corners that couple a bottom panel with side and end wall panels. When the container is erected from the knocked-down-flat state, the assembler need only pull on (or otherwise relatively displace) one of the panels, which pulls all of the panels into a rectilinear shape. In another commonly owned pending patent application Ser. No. 09/253,822, filed Feb. 19, 1999, an integral blank container including end walls with spaced inner and outer end wall panels and an upper/edge is disclosed. Advantageously, the end wall panels and ledge encompass hollow erectable support columns that are associated with upwardly protruding stacking tabs. The internal hollow columns, which are supported by folded and glued panels and are opened under the ledge when the container is in an erected state, vertically reinforce the end walls of the container.
U.S. Pat. No. 4,899,929xe2x80x94Grollman, discloses self-erecting bottom flaps connected to container side walls by folded-back glued gusset panels. The gusset panels are arranged to pull the bottom flaps downwardly into a position perpendicular to the side walls when the side and end walls are unfolded from one another during manual expansion of the container from a flattened parallelogram into a rectilinear box.
The foregoing applications also disclose locking tab structures in which a plural thickness tab protrudes upwardly from the structure of the container end wall to engage in an opening in a similar container stacked thereon. One objective of cartons or containers as described is to support the products that have been loaded into the containers, as well as to bear the load of additional containers that may be stacked on a given container. For this purpose, the panels that are folded and glued can include wall panels having multiple thicknesses of glued-together material and/or partition walls that extend between opposite side walls or end walls. These structural reinforcing features add to the vertical stacking strength or load bearing capacity of the container, namely the maximum vertical weight that can be borne without buckling or displacing the container walls. A container should have good vertical stacking strength, but if possible such stacking strength should be achieved without unnecessarily adding weight to the container and without complicating assembly or erection steps. It is also advantageous if stacking strength can be achieved by means of reinforcements that occupy very little of the space that would otherwise be available for carrying product. Thus, considerations of container strength are sometimes at odds with considerations of weight and volume or ease of assembly.
Containers are routinely stacked vertically to make efficient use of space, and may be reinforced against vertical crushing by employing multiple thickness of material for wall panels or by forming columns, for example as in U.S. Pat. No. 5,330,094xe2x80x94Merz. Known structures that are reinforced in this manner are constructed using added-in insert pieces or using a container structure that requires various manual operations in order to install or erect the reinforcing structure.
Two or more containers are often stacked in vertical registry to be carried manually, to be stacked in a storage area or for shipping on a pallet or the like, in any number of adjacent columns or in a staggered overlapping arrangement resembling masonry. Stacking maximizes the density of storage, and often enables a group of containers to be handled conveniently as a structural unit, e.g., when using a fork-lift truck or a two wheel hand dolly.
Containers in stacks can be subjected to various vertical and lateral forces. Vertical compression force is applied by the weight of upper containers in a stack and the product they contain. This vertical force is borne by the vertically extending structural elements of the underlying cartons. The structural elements that bear vertical forces on a carton or similar container normally occupy only a very limited span of lateral width and/or depth. For example, the vertical forces on many cartons are borne exclusively by their vertical side and end walls. If the stacked cartons remain in registry, then the weight of each upper container is coupled, by the side and end walls of the upper container, to the corresponding side and end walls of an underlying container aligned with the upper container. The side and/or end walls of the upper and lower containers are disposed directly over and under one another over a lateral width and depth of each wall (normally one thickness of material).
If the stacked containers become displaced from exact registry, vertical support may be lacking. It is possible to enlarge the lateral width and depth of the side or end walls of a container such that a ledge is defined on which an upper container may rest. Thus support is provided up to a certain amount of misalignment in the container stack equal to the width of the ledge. Examples of ledge structures are disclosed in the foregoing Sheffer applications. Registry tabs are also provided in U.S. Pat. No. 5,839,650xe2x80x94Sheffer. However, it is difficult to arrange for a ledge in a manner that is consistent with the objectives of fold-and-glue cartons, for example, to provide a knocked-down-flat pre-erection blank for shipping that can be erected with a minimum of manual actions, to conserve container volume of product, and to ensure adequate vertical stacking strength. It would be advantageous if these objectives could all be balanced to provide an optimal container.
The present invention, as in the Sheffer pending applications, provides a site-erected container or carton that is at least substantially formed wholly from an integral flat blank. The only assembly required is erection from a knocked-down-flat configuration by folding the end walls into position to lock into the bottom panel. In so doing, the end and side walls are simultaneously erected perpendicular to the bottom panel. The end walls are provided with registry tabs on a stacking ledge, and are reinforced. The container is supplied with substantially all its joints pre-attached but in a knocked-down-flat state. The container can be produced automatically using a fold-and-glue container production machine, for example as available from Bobst Group, Inc., 146 Harrison Avenue, Roseland, N.J. 07068 (affiliated with Bobst, S A, Lausanne, C H). At the loading site the user need only fold the end panels into place, fill the container and press down the top flaps to produce a stackable unit that is readily handled, stacked on a pallet, or otherwise processed for storage or shipment.
It is an object of the invention to structure a fold-and-glue knocked-down flat container blank so as to improve the vertical stacking strength of the erected container while also decreasing the reliance on correct registry of the containers by manual action.
It is another object to provide hollow vertical reinforcing columns in the end or side walls of a container, which columns are erectable from a folded flat configuration during erection of the container.
It is an object to minimize the manual steps needed to erect the container as described, in particular to cause the end and side walls of the container to erect into a vertical position and the hollow vertical columns to open and deploy, simply by folding end wall flaps inwardly over the columns to lock on the inner bottom wall of the container.
It is a further object to deploy a protruding registry tab when folding the end wall flaps inwardly, to place the registry tab at a space from the outer end walls of the container, and to use the registry tab not only as a structure for engaging with the underside of a next higher container in a stack, but also as a barb against which the free edges of the sidewall flaps can be locked for a lidded closure.
It is another object of the invention to structure a fold-and-glue knocked-down flat container blank so as to improve the vertical stacking strength of the erected container by providing structural support to the sidewalls of the container while also decreasing the reliance on correct registry of the containers by manual action.
It is a further object to minimize the manual steps needed to erect the container as described, in particular to cause the end and side walls of the container to erect into a vertical position, simply by folding end wall flaps inwardly to lock on the inner bottom wall of the container while deploying sidewall support structures.
These and other objects are accomplished in one embodiment of the invention by a container made in a collapsed configuration with bellows fold corners for self-erection, having spaced-panel end walls encompassing hollow columns for vertical reinforcement. An outer end wall panel is joined to the container bottom, leading to a ledge panel that is horizontal when the container is erected, and an inner end wall panel folds over and down to lock via tabs into openings in the bottom. Hollow columns reside under the ledge panel and are provided by column-forming panels folded inwardly and glued at key points to the inner end wall panels such that the hollow columns are pressed open when the inner end wall panel is folded inwardly and is disposed between the front and rear walls. Score or fold lines define the corners of each hollow column, and are placed to bear against inner sides of the front and back walls, which hold the hollow columns open when the container is erected. The column-forming panels have protruding tabs that are backed by corresponding tabs located on the ledge panel between inner and outer panels of the end walls. These tabs join to form a two thickness registration tab that is used to engage a corresponding opening in the container bottom when two or more containers are stacked together. The registration tab is barb shaped, having laterally opposite stepped edges dimensioned and located such that edges of the top panel flaps pass resiliently and are locked down by the stepped edges when the top panel flaps are folded downwardly to engage the registration tab. The container can be made entirely automatically in a knocked-down-flat state by application of glue and folding at the appropriate lines, and can be erected in a single two-handed motion.
In an alternative embodiment of the invention, a container is provided that is made in a collapsed configuration with bellows fold corners for self-erection, having spaced-panel end walls and resilient wing panels for vertical and lateral reinforcement of the containers sidewalls. An outer end wall panel is joined to the container bottom, leading to a ledge panel that is horizontal when the container is erected, and an inner end wall panel folds over and down to lock via tabs into openings in the bottom. The resilient wing panels reside at the outer peripheral edges of the inner end wall panel, and are provided by partially prescoring and pre-creasing a panel flap. In this way, each panel flap may be folded back upon itself and a portion of the inner surface of the inner end wall panel along the partially scored portion of the flap so as to form a wing panel. As a result, the wing panel may be bent along the pre-crease so that the wing panel is partially folded along the pre-crease. The wing panel contributes to the stacking strength of the container and is folded to a right angle rather than being opened into a hollow shape, by pressure from the front and rear walls. The outer end walls have protruding tabs on the inner panel of each end wall. These tabs join to form a single thickness registration tab that is used to engage a corresponding opening in the container bottom when two or more containers are stacked together. The registration tab is also barb shaped, having laterally spaced stepped edges dimensioned such that edges of the top panel flaps pass and are locked down by the stepped edges when the top panel flaps are folded downwardly to engage the registration tab. The container can be made entirely automatically in a knocked-down-flat state by application of glue and folding at the appropriate lines, and is erected in a single motion.